Respiratory syncytial (RS) virus has been reported to encode 2 or 3 nonstructural proteins. At least one of these, henceforth referred to as NS2, was shown earlier to be encoded by a distinct transcript. This finding is based on the identification of several independent cDNA clones that hybrid selected mRNA that was translated in vitro to yield NS2 as its sole translation product. A cDNA insert from the largest recombinant plasmid encoding this gene has been sequenced. The cDNA insert has approximately 1050 bp of RS viral sequence and is about 350 bases larger than the mRNA encoding this protein as determined by Northern blot analysis. Analysis of the DNA sequence revealed two different open reading frames, encoding polypeptides with 137 or 123 amino acids. In one reading frame, translation starts about 50 nucleotides from 5 feet end of the messenger strand and stops 400 nucleotides downstream. In this reading frame there is an untranslated sequence of about 580 nucleotides between the stop codon and the poly (A) tail. In the other reading frame translation starts about 570 nucleotides from the 5 feet end and ends 387 nucleotides downstream, 90 nucleotides short of the poly (A) tail.